<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>媒体查询+rem实现元素变化</title>
</head>
<style>
    * {
        margin: 0;
        padding: 0;
    }
    /* html{
         这种是写死的 
        font-size: 100px;
    } */
    /* 从小到大 */
    
    @media screen and(min-width:320px) {
        html {
            font-size: 50px;
        }
    }
    
    @media screen and(min-width:640px) {
        html {
            font-size: 100px;
        }
    }
    
    .top {
        height: 1rem;
        font-size: .5rem;
        background-color: green;
        color: #fff;
        text-align: center;
        line-height: 1rem;
    }
</style>

<body>
    <div class="top">购物车</div>
</body>

</html>